Treating surfaces with fluids



May 30, 1967 P. J. GOOD 3,322,053

. TREATING SURFACES WITH FLUIDS Filed April 30, 1964 2 She'ets-Shet 1 w 'May 30, 1967 3 P. J. GOOD 3,322,053

TREATING SURFACES WITH FLUIDS Filed A ril 30, 1954 FIG.12 v 1 H643 2 Sheets-Sheet 2 3,322,053 TREATING SURFACES WITH FLUIDS Paul J. Good, Springwater, N.Y., assignor, by mesne assignments, to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Apr. 30, 1964, Ser. No. 363,943 10 Claims. (Cl. 95-89) The present invention relates to the treatment of surfaces with fluids, such as the treatment of sensitized and exposed photographic film or paper with developers or other photographic processing fluids, thus being especially useful in the field of photography, but many features of the invention are not necessarily confined to the field of photography.

An object of the invention is the provision of a generally improved and more satisfactory apparatus for treating surfaces with fluids, particularly useful in connection with the processing of photographic film or paper.

Another object is the provision of a generally improved and more satisfactory method for treating surfaces with fluids, especially for treating photographic film or paper with processing fluids.

Still another object is the provision of a simple and inexpensive and compact form of apparatus, sufliciently small to be built into a photographic camera, for example, or to be used as a small piece of equipment separate from a camera, whereby photographic film or paper or any other suitable form of photographic sheet material may be readily treated with the necessary processing fluid.

A further object is the provision of a simplified and quick method for treating a photographic sheet, particularly suitable for use in a photographic camera.

These and other desirable objects may be attained in the manner disclosed as an illustrative embodiment of the invention in the following description and in the accompanying drawings forming a part hereof, in which:

FIG. 1 is a longitudinal or axial section through one form of apparatus according to the present invention, the section being taken approximately on the line 1-1 of FIG. 2;

FIG. 2 is a transverse section through the same, taken approximately on the line 2-2 of FIG. 1;

FIG. 3 is a section similar in general to FIG. 2, illustrating a modified form of the invention, the section being taken approximately on the line 3-3 of FIG. 4;

FIG. 4 is a fragmentary radial section taken approximately on the line 44 of FIG. 3;

FIG. 5 is a section similar to FIGS. 2 and 3, illustrating a third embodiment of the invention, the section being taken approximately on the line 55 of FIG. 6;

FIG. 6 is a fragmentary radial section taken approximately on the line 66 of FIG. 5

FIG. 7 is a face view of a sheet which is to be treated with liquid (e.g., a photographic sheet to be treated with a processing liquid) together with a capsule of processing liquid and means for distributing the liquid over the sheet which is to be treated, according to still another embodiment of the invention;

FIG. 8 is a longitudinal section taken on the line 88 of FIG. 7;

FIG. 9 is a fragmentary transverse section taken approximately on the line 99 of FIG. 8;

FIG. 10 is a front elevational view of a treating cylinder adapted to receive the sheet structure of FIGS. 7-9;

FIG. 11 is an end elevation of the same;

FIG. 12 is a transverse section through the cylinder of FIGS. 10 and 11, showing the sheet structure in one position therein, just before the capsule of treating liquid is broken; and

FIG. 13 is a view similar to FIG. 12 showing the parts approximately United States Patent .applied forms one wall of moved to a different position to break the liquid capsule ;termediate transfer sheet so as to distribute the treating liquid on the sheet to be treated.

In the treatment of a sheet with a fluid, particularly with a liquid, there is often a problem of spreading a relatively small quantity of the fluid quickly and evenly over a rather large area of the sheet which is to be treated. This problem is particularly severe in the field of photography, where it may be desired to obtain a photographic negative or a photographic print very quickly after an exposure is made, and where the space requirements demand that the equipment be extremely compact, particularly if 'the device for applying the fluid to the sheet is built into a small hand camera or is intended to be a small accessory of a size conveniently held in a persons hand.

Various arrangements have been proposed inthe past,

and have usually involved either a squeezing action or a ciples of capillary attraction to provide the desired quick and even distribution of the fluid. To this end, the invention provides a grooved member having a multiplicity of small capillary grooves therein, the grooved member being either in direct contact with the surface of the sheet which is to be treated, or in contact with an intermediate transfer sheet to which the fluid is first transferred, the fluid then passing through the transfer sheet to the ultimate surface which is to be treated. In either case, the grooved member has a multitude of closely spaced fine grooves inscribed or molded therein, which grooves intersect a channel or conduit through which the treating fluid may be introduced in a Way so that some of the fluid reaches each groove. The grooves in the grooved member are open on one side, and the open side of each groove is, in effect, closed by the surface of the sheet to be treated or the surface of the intermediate transfer sheet, as the case may 'be, thus making each groove into a tiny capillary passageway. When the treating fluid is introduced into the distributing channel or conduit, it reaches each separate capillary passageway or capillary tube, and is quickly drawn by capillary attraction through the entire length of the capillary passageway or tube. Since the capillary passageways are closely adjacent to each other in a lateral direction and since the surface to which the fluid is to be each capillary passageway, it is apparent that the treating fluid will be quickly dis tributed to the entire desired area of the surface to which the fluid is to be applied, whether this be the surface of ultimate treatment, or whether it be the surface of an inwhich will im'bibe the treating fluid and pass it on to the ultimate surface.

Referring now to the form of the invention shown in FIGS. 1 and 2, there is a cylinder indicated in general at 21,

having at one end a radially outwardly extending flange 23 constituting a knob or finger piece by which a cylinder may be turned within the hollow cylindrical housing or casing 25, the inner surface of which is closely adjacent the outer surface of the cylinder 21, with just enough space between them to accommodate snugly the thickness of the sheet S which is to be treated. When the knob 23 is turned to rotate the cylinder within the housing 25, the sheet S is drawn into or thrust outwardly from the housing (depending upon the direction of rotation) in a generally tangential direction, through a tangential slot 27 in the housing. A small radial slot 29 is provided in the cylinder 21, to receive the folded over end of the sheet S as seen in FIG. 2, to couple the sheet to the cylinder to insure joint motion thereof.

Both the housing and the cylinder are conveniently formed of molded plastic material, although other materials could be used if desired. The surface of the cylinder 21 is formed with a great multiplicity of tiny grooves extending in a circumferential direction, from an axially extending distributing channel 33 around most of the circumference, terminating at the point 35 (FIG. 2) just short of the slot 29. These grooves 31 need not be formed throughout the entire length of the cylinder 21, but are formed throughout that part of the length of the cylinder which corresponds to the width of the sheet S which is to be treated. If the extreme edges of the sheet do not need to be treated, then no grooves are formed at the extreme ends of the cylinder 21, as seen in FIG. 1.

These grooves, of capillary size, may be either molded in or inscribed into the surface of the cylinder 21. They are preferably of approximately triangular cross section, with the circumferential wall between two adjacent grooves likewise of triangular cross section, coming to a point at the surface, so that every part of the area of a sheet laid on the grooves will be in communication with one of the grooves. This applies, of course, to the entire area of the sheet which overlies the grooved part of the cylinder, and does not apply to the lateral margins or end margins of the sheet, which do not overlie the grooved part of the cylinder, and which are not intended to be treated.

The liquid for treating the surface may be contained within a collapsible capsule 41 having a nozzle 43 which may be inserted through a normally closed slit or opening in an elastomeric disk 45 which serves as a closure for a small chamber 47 in the exposed end of the cylinder. This chamber communicates by an inclined passageway 49 with the distributing channel 33. Other means of introducing the processing liquid or fluid into the distributing channel 33 may be used, of course, the means just described being merely a convenient example.

In practice, the housing or casing 25 may be built into the body of a photographic camera, or may be in the form of an accessory to be used separately. If built into the camera, the sensitized sheet S will initially be in exposure position lying in the focal plane of the camera, with only the bent over forward end of the sheet extending into the radial slot 29 of the cylinder, and with the rest of the sheet passing out through the tangential slot 27 to exposure position. After the exposure has been made, the user will grasp the knob 23 on the accessible end of the cylinder 21 and will turn the cylinder in a clockwise direction through approximately one full turn or slightly less than one full turn, to draw the exposed area of the sheet S into the housing 25, in a position wrapped tightly around the periphery of the cylinder 21, so that the entire exposed area of the sheet is brought into close overlying relation to the multitude of tiny capillary grooves 31 on the periphery of the cylinder. Then the treating fluid is introduced, either by inserting the nozzle 43 of the capsule 41 into the elastomeric disk 45 and squeezing the capsule, or in any other desired manner. The fluid, passing along the passageway 49 to the distributing channel 33, enters the capillary grooves and is immediately spread evenly and quickly throughout the entire area of the sheet which covers the capillary grooves.

After the required time interval of treatment, which may vary from a few seconds to a minute or more, depending upon the character of the sheet S and the character of the treating fluid, the sheet may be withdrawn from the treating apparatus, either by pulling on the exposed terminal margin of the sheet, or by turning the knob 23 in a reverse direction. The sheet may then be subjected to any further processing required, if any, and it forms a photographic negative or photographic print or other desired, photographic element.

The details of the photosensive coating on the sheet S and the details of the treating fluid are not important for purposes of the present invention, since many forms of photosensitive coating and many forms of treating fluids are well known in the art. The present invention relates to the method of applying the treating fluid and to the apparatus or equipment for applying it, rather than to the exact nature of the treating fluid itself or the nature of the sheet which is to be treated.

FIGS. 3 and 4 show a similar arrangement, modified to use a transfer sheet between the sheet which is to be treated, and the capillary grooves in the cylinder. The transfer sheet is indicated at T. It lies between the sheet S which is to receive the processing treatment, and the periphery of the cylinder 21 containing the capillary grooves. Thus, when the processing fluid is introduced into the distribution channel 33 and from this channel into the ends of the capillary grooves 31, the fluid drawn by capillary attraction through the grooves 31 engages the inner face of the intermediate sheet or transfer sheet T, and is imbibed into this sheet T, going through this sheet to the outer or far side of the transfer sheet where it comes in contact with the inner face of the sheet S which is the ultimate sheet to be treated.

Preferably the intermediate sheet T is made of some material which serves to retain the processing fluid and distribute it laterally. The kind of paper known in the paper trade as rope paper is found to be suitable for this purpose. Also a good grade of blotting paper is suitable, and :many other materials having similar characteristics are likewise suitable.

The intermediate sheet T really serves two purposes. First, it serves as a mechanical protection for the adjacent sensitive face of the sheet S which forms the ultimate article to be treated, protecting the sheet S from possible abrasion or deformation which might occur if the face of the sheet S were pressed tightly against the relatively sharp ridges between the respective capillary grooves 31 on the cylinder 21. This may be particularly important if the sheet S is delicate when in a wet condition. Second, the intermediate sheet T serves also to promote thorough and even distribution of the processing fluid to all desired parts of the face of the sheet S. When the sheet S is in direct contact with the capillary grooves, very good distribution results. are obtained. Nevertheless, any possible failure of the processing fluid to react thoroughly with the surface of the sheet S at the points where the sheet S touches the ridges between the capillary grooves, is obviated by using the intermediate sheet T. Just as a single drop of water or ink placed on a piece of blotting paper quickly spreads laterally to wet the blotting paper through a much larger area than the original area of the drop, so here the processing fluid presented to the intermediate sheet T by the capillary grooves will quickly spread laterally to cover any possible tiny dry spot or partially dry spot over one of the ridges between two adjacent capillary grooves. In fact, the spreading action will even give satisfactory distribution of the processing fluid if one particular capillary groove is accidentally clogged by foreign matter therein. The fluid provided by the adjacent capillary grooves on either side of the clogged groove will spread laterally in the transfer sheet T, to wet that part of the area which is over the clogged capillary groove. Thus the transfer sheet, in turn, will properly distribute the processing fluid throughout the entire intended area of the sheet S which is to be treated.

At the extreme end of the transfer sheet T, a pressure sensitive adhesive pad 55 is preferably provided on its inner face, as seen in FIG. 3. Thus when the sheet material is wound completely into the treating device, to the position shown in FIG. 3, the pressure sensitive adhesive side of the pad 55 will make contact with the outer or back face of the sheet S. Then when the exposed end of the sheet S is drawn tangentially out of the treating device, after the required treatment interval, the adhesion of the outer end of the sheet T to the back of the inner end of the sheet will cause the sheet T to strip away from the sheet S as the latter is drawn out, so that the desired treated face of the sheet S will be presented in condition ready for use, without requiring the user to perform a separate operation of stripping an overlying sheet T away from it.

The processing fluid may be supplied to the distribution channel 33 by means of a capsule in exactly the same'manner as described in connection with FIG. 1. On the other hand, both here in FIGS. 3 and 4, and in the previous device illustrated in FIGS. 1 and 2, the processing fluid may be introduced in any other convenient manner. For example, instead of having an opening in the end of the cylinder as in FIG. 1, there can be a radial opening 57 at one point in the wall of the housing or casing 25, in such a position that when the cylinder has been turned to its final rest position to draw the sheet material into the housing, this radial opening 57 in the housing will be opposite the distribution channel 33, as seen in FIGS. 3 and 4. The sheets S and T can be provided with small openings so positioned that they will likewise be alined with the opening 57 when the cylinder has been turned to its final limit position. These openings will be in the margin of the sheet S, beyond the picture area, so will not interfere with the picture. Then the processing fluid may be introduced through the radial opening 57, by any suitable convenient means such as the nozzle 59 connected to a supply of processing fluid. At the proper moment, the nozzle 59 is thrust radially into the opening 57 and the required quantity of fluid is discharged through the holes in the sheets S and T, and into the distribution channel 33, from which it flows into the capillary grooves 31 as already described.

All other parts of the structure shown in FIGS. 3 and 4 may be the same as already described in connection with FIGS. 1 and 2, and are designated by the same reference numerals.

In FIGS. 5 and 6, there is shown a modification which is similar to what has been described in connection with FIGS. 3 and 4, except that the capillary grooves are not formed directly on the surface of the cylinder 21, but are formed on a separate plastic sheet 61 which is drawn into the cylindrical housing 25 along with the sheets S and T (or along with the sheet S, if no intermediate sheet T is used). In such a construction, the outer face of the cylinder 21 is smooth instead of having the capillary grooves formed therein, and the inner face of the supplementary capillary sheet 61 is likewise smooth. The outer face of the sheet 61 is molded or inscribed with the multiplicity of tiny capillary grooves, like those formed directly on the cylinder 21 in the previous embodiments, these grooves preferably being formed in a direction which will be circumferentially of the cylinder 21 when the supplementary sheet 61 is wrapped around the cylinder.

The primary distribution channel, to convey the processing fluid to all of the capillary grooves, is here formed by a depression 65 molded into the plastic sheet 61, as best seen in FIG. 5, this depression forming a groove extending in an axial direction, and being received in an axial groove 67 former in the cylinder 21 in order to provide the space for this groove 65 in the plastic sheet. Thus when the nozzle 59 is thrust into the radial opening 57 in the housing, and delivers processing fluid through this opening, the fluid passes through the alined holes in the sheets S and T, and into the longitudinal or axial distribution channel formed by the depression 65 in the plastic sheet 61. From there, the processing fluid is distributed circumferentially by capillary attraction, through the capillary grooves 63 on the outer face of the plastic sheet 61, so that the fluid comes into contact directly with the desired part of the area of the sheet S if no intermediate transfer sheet is used, or with the desired part of the area of the transfer sheet T if such a sheet is used, then passing through the thickness of the sheet T with improved lateral distribution therein and wetting thedesired surface area of the sheet S.

In other respects the construction and operation are the same as previously described, and the same reference numerals are used for parts which are not changed.

A modification of the invention, still employing the same principles, is illustrated in FIGS. 7-12. Referring first to FIGS. 7-9, there is here shown a structure which may conveniently be called a pack, comprising the photosensitive sheet 71 which is to be treated (corresponding to the sheet S in the previous embodiments) and the plastic capillary sheet 73 (corresponding to the plastic sheet 61 in the embodiment of FIGS. 5 and 6) and, if desired, an intermediate sheet or transfer sheet 75 (corresponding to the sheet T in the privious embodiments). The face of the plastic sheet 73 which is faced toward the intermediate sheet 75 (or toward the ultimate sheet 71, if no intermediate sheet is used) is molded or inscribed with the closely adjacent capillary grooves such as described in connection with the previous embodiments, these grooves being preferably of triangular crosssection and closely adjacent to each other so that the material between the grooves is preferably triangular, terminating in relatively sharp ridges, whereby substantially the entire area of the next sheet 75 will be subjected to the action of liquid within the capillary grooves 73. These capillary grooves run in a direction lengthwise of the capillary sheet 73, and extend into a transverse distribution channel 77 formed by a transverse depression molded into the plastic sheet 73, like the molded part 65 in the previous embodiment.

At one end of the plastic capillary sheet 73 there is a breakable or frangible capsule 81 containing the processing fluid. This lies on the same face of the sheet 73 as the distribution channel 77 and the capillary grooves 74. Thus if the capsule 81 is broken, the processing fluid will flow from the capsule into the transverse distribution channel 77, and since all of the capillary grooves 74 open into this channel 77, the processing fluid will be supplied to the ends of all of the grooves 74, where it will be quickly moved along the grooves by capillary attraction, to wet the adjacent face of the sheet 71 if no intermediate transfer sheet is used, or to wet the transfer sheet 75, if one is present, andbe betterdistributed thereby and pass through the transfer sheet 75 to the adjacent face of the sheet 71, in a manner similar to that described in connection with the previous embodiments.

A piece of pressure sensitive adhesive tape 85 is preferably attached to the capillary sheet 73 at one end, as seen in FIG. 8. This is initially protected by an overlying layer 87 or paper which is stripped off before loading into the treating appliance. At the opposite end of the pack, the sheet 71 is transversely scored at 91 to provide an end marginal portion 93 which can easily be bent at an angle to .the main body of the sheet, for insertion in the radial slot of the cylinder in the treating device.

The treating device itself comprises the hollow cylindrical housing or casing 101 corresponding closely to the housing 25 in the embodiments previously described, and the cylinder 103 rotatably mounted within the housing 101, with a knob 105 at one end, to be grasped in order to turn the cylinder. The cylinder has a radial slot 107 into which the marginal portion 93 of the sheet 71 may be thrust when the device is being loaded for a treatment operation. Then when the knob is rotated, the pack is drawn into the cylindrical housing 101 through the tangential mouth or slot 111, the capsule 81 of processing fluid being near the trailing end of the pack. FIG. 12 shows the parts just as the capsule 81 reaches the mouth slot 11, and starts to enter the treating apparatus. It will be seen that the cylinder 103 is not circular in cross section, but is circular throughout most of this periphery with a depressed or relieved portion to accommodate the capsule 81.

As the capsule is drawn further into the treatment housing, by continued rotation of the cylinder 103 from the position shown in FIG. 12 to that shown in FIG. 13, the capsule becomes squeezed between the cylinder and the surrounding housing sufficiently to break or rupture the capsule, releasing the processing fluid contained therein so that the fluid flows to the lateral distribution channel 77 and thence to the capillary grooves 74, where it is distributed quickly and evenly in the same manner previously described in connection with the previous embodiments, either directly to the face of the sheet 71 if no intermediate transfer sheet is used, or to the transfer sheet 75 if one is employed, then passing through the porous transfer sheet to the sheet 71.

When the protruding end of the sheet 71 is grasped to draw it out of the treating device, the pressure sensitive adhesive tape 85 will cause the capsule and the connected plastic capillary sheet 73 and intermediate sheet 75 to adhere to the anchored end of the sheet 71 which is still on the cylinder 103, so that the main body of the sheet 71 is automatically stripped away from the discharged capsule and from the sheets 73 and 75, as the now treated sheet 71 is drawn out of the device.

In some cases, the photosensitive side or face of the sheet which is to be treated may be the side which is faced toward the capillary structure and which receives the processing fluid from the capillary grooves or from the intermediate transfer sheet. In other cases, the photosensitive side may be the far side of the sheet which is to be treated, so that the processing fluid passes through the sheet to be treated before reacting with the emulsion or photosensitive part thereof. It is immaterial for purposes of the present invention which side of the sheet is the photosensitive side.

It is seen from the foregoing disclosure that the objects and purposes of the invention are well fulfilled. It is to be understood that the foregoing disclosure is given by way of illustrative example only, rather than by way of limitation, and that without departing from the invention, the details may be varied within the scope of the appended claims.

What is claimed is:

1. Apparatus for wetting a sheet with a processing fluid, comprising means forming a capillary groove structure including a substantially cylindrical convex surface shaped to provide a multiplicity of small capillary grooves extending in one direction parallel to each other in close side by side relationship, said surface being shaped to provide also a distribution channel extending transversely to the capillary grooves and communicating with all of said grooves, means substantially enclosing said convex surface for holding the sheet to be wetted in a position wrapped around a major portion of the periphery of said convex surface and in substantially stationary contact against said surface of said capillary groove structure, and means for supplying fluid to said distribution channel to flow therefrom to said capillary grooves and thence by capillary attraction along said grooves to wet the overlying surface of the sheet.

2. Apparatus as defined in claim 1, wherein said grooves are of substantially triangular cross section and wherein the walls between adjacent grooves are in the form of sharp pointed ridges.

3. Apparatus as defined in claim 1, wherein the sheet to be wetted is a photographic sheet to be processed.

4. Apparatus for wetting a sheet with a processing fluid, comprising means forming a capillary groove structure including a surface shaped to provide a multiplicity of small capillary grooves extending in one direction parallel to each other in close side by side relationship, said surface being shaped to provide also a distribution channel extending transversely to the capillary grooves and communicating with all of said grooves, and means for supplying fluid to said distribution channel to flow therefrom to said capillary grooves and thence by capillary attraction along said grooves to wet an overlying surface of a sheet, and means for holding the entire area to be wetted of said sheet to be wetted in simultaneous stationary contact with said capillary groove structure during the supplying of fluid to said distribution channel.

5. Apparatus for wetting a sheet with a processing fluid, comprising means forming a capillary groove structure including a surface having a multiplicity of small capillary grooves extending parallel to each other in close side by side relationship and a distribution channel extending transversely to the capillary grooves and communicating with all of said grooves, means for holding the sheet to be wetting against said surface of said capillary groove structure, and means for supplying fluid to said distribution channel to flow therefrom to said capillary grooves and thence by capillary attraction along said grooves to wet the overlying surface of the sheet, and a photographic sheet to be processed, said sheet to be wetted being an intermediate sheet interposed between said photographic sheet and said capillary groove structure so that the fluid is transferred from the capillary groove structure to the sheet to be wetted and then through the sheet to be wetted to the photographic sheet.

6. Apparatus for wetting a sheet with a processing fluid, comprising means forming a capillary groove structure including a surface having a multiplicity of small capillary grooves extending parallel to each other in close side by side relationship and a distribution channel extending transversely to the capillary grooves and communicating with all of said grooves, means for holding the sheet to be wetted against said surface of said capillary groove structure, and means for supplying fluid to said distribution channel to flow therefrom to said capillary grooves and thence by capillary attraction along said grooves to wet the overlying surface of the sheet, said means for holding the sheet against said capillary groove structure including a housing of approximately hollow cylindrical shape and a core member of approximately cylindrical shape rotatable within said housing.

7. A construction as defined in claim 6, wherein said multiplicity of small capillary grooves are associated with said core member to turn therewith in relation to said housing.

8. A construction as defined in claim 6, wherein said multiplicity of small capillary grooves are formed directly on the periphery of said core member. I

9. A construction as defined in claim 6, wherein said multiplicity of small capillary grooves are formed on a plastic sheet separate from said core member and attachable to said core member to be wrapped around the periphery of said core member within said housing.

10. The method of wetting a sheet with a processing fluid which comprises the steps of providing a sheet to be wetted, providing a substantially cylindrical hollow housing having an approximately tangential slot extending axially along one side thereof, providing a capillary groove structure of approximately cylindrical form rotatable within said housing, coupling one end of said sheet to said groove structure and rotating said groove structure within said housing to draw a substantial part of said sheet into said housing through said slot and to cause said part of said sheet to be wrapped around said groove structure in contact therewith and supplying processing fluid to the capillary groove structure so that the fluid will be drawn through the grooves thereof by capillary attraction and will wet the sheet in contact therewith, and maintaining the sheet and the capillary groove structure in stationary relation to each other throughout the wet ting of the entire sheet area which is to be wetted.

References Cited UNITED STATES PATENTS 6/1941 Van der Grinten -89 8/1952 Nagels et al. 9589 

1. APPARATUS FOR WETTING A SHEET WITH A PROCESSING FLUID, COMPRISING MEANS FORMING A CAPILLARY GROOVE STRUCTURE INCLUDING A SUBSTANTIALLY CYLINDRICAL CONVEX SURFACE SHAPED TO PROVIDE A MULTIPLICITY OF SMALL CAPILLARY GROOVES EXTENDING IN ONE DIRECTION PARALLEL TO EACH OTHER IN CLOSE SIDE BY SIDE RELATIONSHIP, SAID SURFACE BEING SHAPED TO PROVIDE ALSO A DISTRUBUTION CHANNEL EXTENDING TRANSVERSELY TO THE CAPILLARY GROOVES AND COMMUNICATING WITH ALL OF SAID GROOVES, MEANS SUBSTANTIALLY ENCLOSING SAID CONVEX SURFACE FOR HOLDING THE SHEET TO BE WETTED IN A POSITION WRAPPED AROUND A MAJOR PORTION OF THE PERIPHERY OF SAID CONVEX SURFACE AND IN SUBSTANTIALLY STATIONARY CONTACT AGAINST SAID SURFACE OF SAID CAPILLARY GROOVE STRUCTURE, AND MEANS FOR SUPPLYING FLUID TO SAID DISTRIBUTION CHANNEL TO FLOW THEREFROM TO SAID CAPILLARY GROOVES AND THENCE BY CAPILLARY ATTRACTION ALONG SAID GROOVES TO WET THE OVERLYING SURFACE OF THE SHEET. 